[Macrophage activation by synthetic peptides. III. Changes in the membrane potential, Ca2+ content and the regulatory decrease of macrophage volume under the action of tuftsin and its antagonist].

With the use of oxonol voltage-sensitive fluorescent dye it has been shown that the stimulation of macrophages (MP) with tuftsin results in a two-phase change in membrane potential: depolarization followed by hyperpolarization of plasma membrane. The pattern of changes in membrane potential depends on Na+ concentration in the medium and is disturbed with binding of cytoplasmic Ca2+. Fluorescent signal obtained from MP loaded with Ca(2+)-activated photoprotein obelin points to a significant increase in the concentration of cytoplasmic Ca2+ under the influence of tuftsin on cells: the source for Ca2+ being the medium. The rate of regulatory voltage decrease in MP increases under the influence of tuftsin: the effect of this peptide being similar to that of calcium ionophore. All these findings taken together enable us to suggest a phenomenological scheme of transmembrane ion signals arising during stimulation of MP with tuftsin: the receptor-mediated calcium channel provides a rise in cytoplasmic Ca2+ which opens non-selective cation channels for Na+ ions to activate eventually Ca(2+)-dependent K(+)-transport.